what you need to know is that these sites (coinmarketcap, coindesk, etc) are all giving you an average price which means they take the price from multiple resources it can even be USD, JPY, CNY,... and convert it all to USD and give an average price.
also another important thing is their update rate. you should check to see how fast each of these update. for example coinmarketcap does it every 5 minutes.
And on top of this, some exchanges have higher rates, but are completely in Chinese, so good luck registering an account if you have to rely on Google translate
I had some Worldcoin left, but I'm getting 10-20% less than Coinmarketcap states it should be worth as the exchanges I can get (easy) access to don't have the high rates others have unfortunately.